package com.droidwatcher.util;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;

import java.io.FileInputStream;
import java.io.IOException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Locale;

/**
 * Md5
 * 提供对字符串的md5-->stringMD5
 * 提供对文件的Md5-->fileMD5
 *
 * 对于大文件，可以使用DigestInputStream
 */
public class Md5Utils {

    protected static char hexDigits[] = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
    protected static MessageDigest messageDigest = null;

    static{
        try{
            // 拿到一个MD5转换器（如果想要SHA1参数换成”SHA1”）
            messageDigest = MessageDigest.getInstance("MD5");
        }catch (NoSuchAlgorithmException e) {
            System.err.println(Md5Utils.class.getName()+"初始化失败，MessageDigest不支持MD5Util.");
            e.printStackTrace();
        }
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {

        char c0 = hexDigits[(bt & 0xf0) >> 4];
        char c1 = hexDigits[bt & 0xf];
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    /**
     * 字符串的md5加密
     * @param input
     * @return
     */
    public static String stringMD5(String input) {
        // 输入的字符串转换成字节数组
        byte[] inputByteArray = input.getBytes();
        // inputByteArray是输入字符串转换得到的字节数组
        messageDigest.update(inputByteArray);
        // 转换并返回结果，也是字节数组，包含16个元素
        byte[] resultByteArray = messageDigest.digest();
        // 字符数组转换成字符串返回
        return bufferToHex(resultByteArray);
    }
    /**
     * 文件的md5加密
     * @param inputFile
     * @return
     * @throws IOException
     */
    public static String fileMD5(String inputFile) throws IOException {
        // 缓冲区大小（这个可以抽出一个参数）
        int bufferSize = 256 * 1024;
        FileInputStream fileInputStream = null;
        DigestInputStream digestInputStream = null;
        try {
            // 使用DigestInputStream
            fileInputStream = new FileInputStream(inputFile);
            digestInputStream = new DigestInputStream(fileInputStream,messageDigest);
            // read的过程中进行MD5处理，直到读完文件
            byte[] buffer =new byte[bufferSize];
            while (digestInputStream.read(buffer) > 0);
            // 获取最终的MessageDigest
            messageDigest= digestInputStream.getMessageDigest();
            // 拿到结果，也是字节数组，包含16个元素
            byte[] resultByteArray = messageDigest.digest();
            // 同样，把字节数组转换成字符串
            return bufferToHex(resultByteArray);
        } finally {
            try {
                digestInputStream.close();
            } catch (Exception e) {
            }
            try {
                fileInputStream.close();
            } catch (Exception e) {
            }
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        //测试字符串MD5加密
        //123456: e10adc3949ba59abbe56e057f20f883e
        //eastcom:  6997c46956185a7c4d452646fc9c69e2
        System.out.println(stringMD5("eastcom"));


        try {
            long startTime = System.currentTimeMillis();
            //测试文件MD5加密
            String FilePath = "D:/ilink_ide.zip"; //4227e9fc4bd71ff34887d47867967b29
            System.out.println(fileMD5(FilePath));

            long endTime = System.currentTimeMillis();
            System.out.println((endTime - startTime)/1000);

        } catch (IOException e) {

            e.printStackTrace();
        }
    }

    /**
     * 参考文章：
     *  http://www.zhihu.com/question/23702510
     *  http://blog.csdn.net/lf_software_studio/article/details/8025497
     *  http://my.oschina.net/laigous/blog/106646
     *  http://blog.csdn.net/wangqiuyun/article/details/22941433
     */

    public   static String SHA1(Context context) {
        try {
            PackageInfo info = context.getPackageManager().getPackageInfo(
                    context.getPackageName(), PackageManager.GET_SIGNATURES);
            byte[] cert = info.signatures[0].toByteArray();
            MessageDigest md = MessageDigest.getInstance("SHA1");
            byte[] publicKey = md.digest(cert);
            StringBuffer hexString = new StringBuffer();
            for (int i = 0; i < publicKey.length; i++) {
                String appendString = Integer.toHexString(0xFF & publicKey[i])
                        .toUpperCase(Locale.US);
                if (appendString.length() == 1)
                    hexString.append("0");
                hexString.append(appendString);
                hexString.append(":");
            }
            String result = hexString.toString();
            return result.substring(0, result.length()-1);
        } catch (PackageManager.NameNotFoundException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return null;
    }

}